The overall efficiency of the laser system is defined as the ratio of the output energy of the laser beam to the input energy of the pumping source.
To maximize the efficiency of an optically pumped laser such as flashlamp pumped solid state or dye laser a laser pumping cavity is used.
The pumping cavity concentrates the light output from the pump source onto the laser material. In addition, in order to achieve a uniform illumination of the lasing material and to eliminate "hot" regions in the laser beam it has been found desirable to surround the pumping cavity with a diffuse-reflector surface. The diffuse-reflective pump cavity surface layer, usually a compressed barium sulfate powder, has been used for the generation of high energy, uniform intensity laser beams in solid state as well as dye laser systems.
Ideally, one would like a large overlap of the pump emitted radiation and the absorption bands of the lasing material. In this way the thermal load and the thermally induced optical distortions in the laser material are minimal. In addition, it is desirable to reduce the ultra-violet Portion of the pump radiation since it may cause solarization of the laser material and deterioration of the organic liquid coolant used for cooling the pump cavity. However, for most conventional pump sources and lasing materials the aforementioned overlap is small A method used in the prior art for increasing the matching between the emission spectrum of the pumping source and the excitation spectrum of the lasing material is based on the use of fluorescent materials dissolved in the liquid coolant used for cooling the pump cavity, see for example U.S. Pat. No. 4,445,217. However, such fluorescent materials--usually of organic nature--are gradually destroyed as a result of the exposure to ultra-violet radiation and degradation in performance results.